: The long range aim of this project is the quantification and interpretation of irregular vocal fold vibration during self-oscillation, relevant for the prevention and treatment of voice disorders. This quantification of irregular oscillations will be accomplished with the aid of multiple-camera high-speed video imaging and excise larynx experiments. Utilizing information imaged from multiple views, 3D trajectories will be tracked for an array of fleshpoints along the superior and medial edges of coronal cross-sections of the folds. Steady-state, transient and irregular vocal fold oscillations will be imaged, and precise 3D reconstructions will be performed. Hypothesized mechanisms of vibrational instabilities will be tested with direct application for the prevention and treatment of voice disorders. Specific aims include: (1) using multiple-camera high-speed video imaging, quantify the 3D oscillations of the folds for a variety of periodic regimes (e.g., oscillations corresponding to chest-like, falsetto-like and fry-like phonations). Contrast the vibratory patterns of the regimes. (2) Quantify vocal fold oscillations during bifurcations (sudden qualitative changes in the vibratory pattern of the folds). Within the framework of nonlinear dynamics, evaluate current hypotheses regarding the physiological mechanisms of these transitions and instabilities. (3) Quantify the eigenmodes, eigenfrequencies, and damping ratios of the folds. To what extent are the phonation frequencies of aim 1 governed by eigenfrequencies? Can the phonatory regimes of aim 1 and the bifurcations of aim 2 be expressed as superpositions of just a few underlying eigenmodes? To what extent can the bifurcations of aim 2 be viewed as desynchronizations of underlying eigenmodes? (4) Evaluate several models of vocal vibration by comparing predicted fleshpoint trajectories with those observed experimentally. Augment the theoretical interpretibility of the data gathered in aims 1-3 by integrating the empirical observations into updated versions of the models. (5) By imposing the same restrictions on the excised larynx set-up as those encountered clinically (limited light, limited space for imaging equipment, imaging from a superior aspect only) adapt the above high-speed 3rd reconstruction techniques for clinical use.